The goal of this project is to understand mechanisms of oocyte maturation and spawning in a model organism, the zebra mussel (Dreissena polymorpha). We have previously shown that serotonin can induce germinal vesicle breakdown (GVBD) and spawning in zebra mussels. Proposed experiments will investigate the hypothesis that GVBD and spawning are mediated by G- protein-coupled serotonin receptor(s) that activates a concerted response involving both inhibition of adenylyl cyclase and stimulation of phospholipase C. Prior supporting data for the hypothesis includes the pharmacology of spawning and GVBD in zebra mussels, which resembles ligand-binding data of 5HT1ym, a cloned molluscan receptor that has sequence similarities to fly and vertebrate serotonin receptors that are coupled to both adenylyl cyclase inhibition and phospholipase activation. Furthermore, in other organisms meiosis reinitiation is inhibited by cyclic AMP, correlated with increases in phospholipase C products, and affected by manipulation of G- proteins. Specific research aims will be to determine primary sequences of zebra mussel gonadal serotonin receptor(s) and G protein(s), to compare ligand binding data for the cloned receptor to spawning and GVBD pharmacology, to assess serotonin receptor location by sequence specific immunocytochemistry and in situ hybridization and by investigating serotonin responses of non- gonadal tissues, and to study roles of G proteins by measuring putative mediating enzymes and second messengers and effects of sequence specific inhibitors. Specific student participation aims; one graduate student and one undergraduate will learn molecular biological techniques, including RT-PCR, gel electrophoresis, cloning, sequence analysis, antibody production, immunohistology, and in situ hybridization; one undergraduate will investigate pharmacology of spawning and GVBD in vivo and in vitro; one undergraduate will investigate effects of serotonin and other chemicals on non-reproductive behaviors of zebra mussels. Students will become expert at one or more techniques, will discuss their experiments with the P.I. frequently, will report on their work at weekly group meetings, will write or participate in the writing of publications on completed work, and will present their results at regional and national meetings, including the annual MBRS Symposium. Thus, as has been successfully accomplished with MBRS and other students, students become actively involved in data acquisition, reduction, analysis, and presentation, and are co-authors of reviewed publications from the laboratory. Health relevance: This project will investigate, in a model system, the most poorly understood mechanisms in the reinitiation of meiosis, the coupling of membrane receptors to the process of GVBD and oocyte maturation. This is relevant to understanding fertility problems. In addition, the serotonin receptor we are investigating resembles to some degree the pharmacology of a receptor that may be involved in the mechanisms of migraine headache treatment.